New gem format and g2c -> f2c fix

[ivanku]

It's now possible to install linalg as a gem using bundler:

Gemfile:

gem 'linalg', git: 'git://github.com/ivanku/linalg'

I also applied the fix that was mentioned here: http://rubyforge.org/forum/forum.php?thread_id=31058&forum_id=1171 (g2c.h -> f2c.h change) to get native extensions to compile (verified on Ubuntu 12.04 64-bit with f2c package installed from standard repository)